Regulations continue to drive the need to improve the combustion process in order to lower pollutant emissions and increase fuel efficiency. The design of the combustion chamber in large bore 2 cycle engines has remained unchanged over the last twenty to 30 years. While there have been advances in areas such as fuel injection, combustion monitoring and control systems; the entire combustion process has not been redesigned to take advantage of new technology. The traditional approach to emissions reduction has been to install pre-combustion chambers (PCC) and new or modified turbochargers on the engines to allow operation at leaner air fuel ratios. In the last decade, high pressure fuel injection has been installed on existing engines to reduce emissions or increase fuel economy. Since the high pressure fuel injection systems use electronically controlled valves to admit the fuel, this allows the designer more freedom when designing the combustion system since the valve does not have to be positioned where it can be easily operated with a camshaft. A fresh look at the design of the combustion chamber that takes advantage of the newly available technologies was in order. At the same time, consideration was given to all aspects of the design to reduce pollutant emissions such as nitrogen oxides, carbon monoxide, unburned hydrocarbon and formaldehyde. In addition to emissions reductions, an increase in fuel efficiency was also desired. In order to control the costs of development, computer modeling was used to evaluate possible designs before prototype parts were built. This allows for shorter cycle times and the ability to evaluate more designs than would be possible by building prototype parts for each design and testing them in the engine. The first engine family that Cameron decided to redesign was the GMV family since this engine represents the largest percentage of large bore, 2 cycle Cooper Bessemer engines and we maintain a GMVH-6 test stand at Southwest Researc